Percussive tool



Nov, 2 1, 1931; A. G. DECKER PERCUSSIVE TOOL Original Filed April 4, 1928 3 Sheets-Sheet 1 (ill! A \g gwvwntoz A. G. DECKER PERCUSSIVE TOOL Original Filed April 4, 1928 3 Sheets-Sheet 2 A. G. DECKER PERCUSSIVE TOOL Nova 2.4, 1931.

Original Filed April 4, 1928 3 Sheets-Sheet 5 ooaxol Ira 01w- Patented as. 24, 1931 UNITED STATES PATENT OFFICE ALONZO G. DECKER, Ol' BALTIMORE COUNTY, MARYLAND, ASSIGNOB TO THE BLACK AND DECKER MANUFAOI'UBING COMPANY, 01 TOWSON HEIGHTS, MARYLAND, .A.

CORPORATION 01 'MABYLAND PEBCUSBIVE TOOL Application fled April 4, 1828, Serial No. 287,148. Renewed October 'I, 1931.

The' invention relates to a power driven percussive tool. The hammer mechanism is of the type in which a striker is eccentrically mounted on a rotary member or carriage, be-

, ing movable relative thereto so that it is held by centrifugal force in a position in which it comes in contact with a transmitter or anvil by which the blow is transmitted to the work. The reaction of the blow causes the striker to swin inwardly toward the axis of the carriage w ereby it clears the anvil or transmitter permitting the carriage or rotary member to continue to revolve without interruption. The centrifugal tendency due to rotation of the carriage returns the striker to its outward or striking position when it has passed the anvil so that the blow is repeated at regular intervals, which are predetermined by the designer and, in accordance with the construction shown, occur once for each revolution of the carriage.

Such percussive tools or hammers, particularly when made of such proportions that the tool is of portable dimensions, have been subi ject to early failure due to the efiect on the mechanism of the rapidly repeated shocks of the hammer blows and the reaction thereof.

The object of'the present invention is to protect the carriage and parts from these peak stresses or shocks and further to protect the gearing and connections from the shocks which are communicated thereto from the carrier and hence back to the driving means.

In the accompanying drawings I have illustrated so much of a percussive tool equipped with the features of the invention as is necessarytoa full understanding of the construction of the device and its operation.

In the drawin s: 1

Figure 1 is a ragmentary elevation show; ing the hammer casing, the same being broken away intermediately to expose the carrier, striker and anvil and a portion of the gearmg. v A

Fig. 2 is a horizontal section onthe line 2-2 of Figure 1.

Figure 3 is a horizontal section on the line 33 of Figure 1.

Figure 4 is an elevation of an entire portable power driven tool embodying the features of the invention illustrated-in Figures 1, 2 and 3.

Figure 5 is an elevation correspondin to Figure 1, the casing being likewise broien away to show the striker and gearing, the mechanism shown being a modification of that shown in the previous fi es.

Figure 6 is a section on t e line 66 of Fi re 5.

eferring to the drawings by numerals, each. of which is used to indicate the same or similar parts in the different figures, the tool, the preferred form of which is illustrated in a general way in Figures '1 to 4, comprises a motor 1 enclosed in a motor housing 2, to one end of which'housing a grip member 3 is secured, the hammer casing or gear casing 4 being secured to the opposite end of the motor housing.

The motor 1 is provided with a motor shaft 5 on which is mounted a bevel gear 6 which meshes with a bevel gear 7 which is mounted on a transverse shaft 8 which rotates in suitable bearings 9 in the casing 4, it being understood that the details thus described relate to the preferredform illustrated and are not regarded as essential.

The bevel gear 7 on the shaft 8 is free to rotate relatively to the shaft 8, being, however, connected by a torsion spring 10 to a pinion 11 which is also mounted to rotate freely on the shaft 8 and meshes with the hammer carriage gear or ring 12, to be described.

In the form of the invention shown, the pinion 11 is preferably made hollow at the center providlng a chamber 14 for the spring 10 which, in the form of the invention shown, is helical, enclosing the portion of the shaft 8 within the chamber 14 and having its respective ends turned oppositely parallel to the axis. One said end 15 is inserted in a suitable hole or depression in the pinion 11 at the bottom of the chamber and the other end 16 is inserted in a similar aperture in the bevel gear 7. These ends 15 and 16 serve as the means for connecting the spring to the pinion and bevel gear respectively.

In the'form of the invention shown, the

striker or hammer to be described, is carried by a carrier membe r or carriage which, in the form of the invention shown, consists of two disks 21 and a connecting portion 22 between the disks, which connectmg portion, in the form of the invention shown, underlies a relatively small ortion of the area of the disks, as indicate in Figures 1 and 3, providing a recess 24 in the carrier between the disks for the operation of the striker or hammer member proper, which is indicated by reference character 25. The hammer or striker 25 is mounted in the chamber or recess 24 on a pin 26, which .is parallel to the axis of the disks 21 and seated at its ends in the disks. The carrier or carriage 20 is provided at each end with a trunnion 27 projecting outwardly from the'center' of each corres onding disk and seated in bearings 13 in t e hammer or gear casing 4, which is suitably chambered at 23 to receive such bear- The hammer or striker member 25 is mounted in the recess or chamber 24 to swing freely about the pin 26. The pin intersects the hammer at a point spaced rom one end by a distance shown as about one-third of the length of the hammer, though the exact proportions are not of great importance, and the short end of the hammer is cut off substantially at right angles to its length, forming a stop surface 28 which engages the stop the hammer with the stop shoulders 29* 'posi- I tions the hammer in the striking or outermost position, shown in Figure 1, in which position the centrifugal action due to rotation of the carriage tends to hold the striker.

In this position of the hammer or striker its outer end 30 rojects outwardly beyond the disks 21 perrmttin it to engage the transmitter or anvil 31, as s own in igure 1.. The transmitter or anvil is, in the form of the invention shown, mounted to slide in the direction of its length, being guided in any suitable manner as by means of a pin 32 projecting upwardly from a shoulder 33 encircling the transmitteroutside the casing, the pin projecting upwardly through a hole 34 'in the casing.

It will be understood from the preceding description of Figure 1 that the carrier rotates to the left as viewed in that figure and the reaction of the hammer or striker 25 after each'blow causes it to rotate right-handedly about the pin 26 until the surface thereof which is uppermost in the striking position shown in Figure-1, hereinafter referred to "as the recoil stop surface 35, contacts the V shoulders 29 on the carrier.

It will be understood that the hammer or striker is carried substantially in this osition until it passes the anvil or transmitter 31, part of this periodbeing taken up by the period of the recoil. After. passing the anvil it again swings out in response to centrifugal force and engages the anvil on the next revolution. I

To ermit the swinging of the hammer. from t e striking osition shown in Figure 1 to the recoil POSltiOll, the stop surfaces 28 and 35 at the rlght near the rear and the top of the hammer as shown in Figure'1, are connected by a curved-portion 36 which is shown as a circular arc concentric with the pin 26, the im ortant feature being thatthe formation 0 this part shall not interfere with the swing of the hammer from the striking position to the recoil position. 1

An important function ofthe invention is the elimination of the shock to the gears and carriage which would be incident to the recoil of the hammer. To this end, in the form 'of the invention shown in Figure 1, the striker or hammer is provided with a cam member 38 presenting a cam surface39 which is eccentric as to the pin 26 about which the hammer or striker swings. This cam surface is engaged .bgla piston or follower 40 mounted in a suite guideway 41 formed in the carrier for this purpose, the same being, as shown, disposed radially as to the axis of the carrier, though the exact arrangement of the follower and guideway are not essential.

The guideway 41, as shown, is in the form of a cylinder closed at the end opposite to the hammer and containing a helical spring 42 which bears at one end against the rear end 43 of said cylinder or aperture and at the other end against the piston or follower 40 which, in the form shown, is cupped or hollowed at 44 to receive the s ring.

By reference to the section, Figures 1 and 3, it will benotedlthat the. cam surface 39 in the recoil "position lies between the stop shoulders 29. l 'i In the form shown,the radius of the cam surface 39 about'thepin 26 on which the striker 25 swings increases tothe left from the stop surface 28-0f1the-striker so that on the recoil the combined action of the cam and follower offers an' increasing resistance to the backward throw of the striker and'the spring form of the device the striker is formed with projecting hub portions 45 about which are wrapped helical tension springs 46. Each of these is seated at one end at 47 in a suitable hole 48 bored through the striker for this purpose parallel to the axis and each of the springs is seated at its opposite end at 49 in one of the disks 21. The arrangement of the springs is such that on the recoil of the striker, tension is applied thereto, in resistance of the spring or springs increasing as the striker approaches the stop shoulders. 29 and, as stated in regard to the first form of the invention, the springs may be so proportioned as to check the striker and reduce the momentum .to zero as the end of the recoil is reached and on the working stroke they deliver stored energy to the hammer.

In order to further protect the gearing, driving mechanism and motor from shocks due to the impact of the hammer on the anvil or transmitting member 31 and the recoil, a resilient member in the form of the spring 10, previously described, is inserted in the driving connections between the motor 1 and the carriage or carrier 20.

The operation of the device will be easily understood from the preamble and description, the important features of the invention being the provision of cushioning means whereby the recoil is checked and the force ofthe recoil is accumulated and added to the working stroke and the further provision of means whereby the otherwise harmful effect of theimpact and reaction of the hammer blows on the driving mechanism, is equalized and cushioned, greatly increasing the life of the driving connections, the motor and particularly the keys, gear teeth, etc.

I havethus described specifically and in detail a preferred and a secondary form of the invention in order that the nature and operation of the device and manner of applying and using the same may be clearly understood, however, the specific terms herein are used descriptively rather than in a limiting sense, the scope of the invention being defined .in the claims.

What I claim as new and desire to secure 7 stroke checking the recoil.

2. The combination in a portable power driven percussive tool of a rotary carrier and means for driving the carrier, a striker pivot ally mounted on the carrier eccentrically thereof to be swung by centrifugal force into striking position, a member in the path of the striker in its advanced position, to reposition the striker at each end of its stroke, a cam member and a spring pressed follower, one on the striker and the other on the car rier, both said members being between said respective stop surfaces, said members cooperating to advance the hammer in its working stroke and retard its reaction stroke.

3. The combination in a percussive tool of a rotary carrier member, a centrifugally operated swinging member mounted thereon, an anvil in the ath of the striker member in its outer position, the recoil serving to return the striker member so that it passes the anvil, and means tending to check and control the recoil of the striker member comprising a cam carried by one said member and a follower carried by the other said member, and resilient means for holding the cam and follower in contact.

4. The combination in a portable power driven percussive tool of a rotary carrier, means for driving the carrier, a striker pivotally mounted on the carrier eccentrically thereof to be swung by centrifugal force into striking position, a member in the path of the hammer in striking position, to receive the blow and transmit the same to the work. a rectilinear stop' surface on the carrier and cooperating stop surfaces on the hammer on an angle to each other to engage the stop surface on the carrier at each end of the stroke, a cam surface on the hammer adjacent the stop surface thereon which operates at the recoil end of the stroke, a moving follower on the carrier engaging said cam and a spring to press the follower into engagement with the cam to check the recoil and to assist in the forward stroke.

Signed by me at Towson, Maryland, this 31st day of March, 1928.

ALONZO G. DECKER.

ceivc the blow and transmit the same to the work, spaced stop surfaces on the carrier 

